Password Strength Checker
Enter Password
A password strength checker uses Shannon entropy to quantify how hard a password is to crack. Entropy measures unpredictability based on character set size and password length — higher is harder to guess.
- 1Entropy (bits) = log₂(charset_size) × length
- 2Charset grows by adding: uppercase (+26), lowercase (+26), digits (+10), symbols (+32)
- 3A 12-character password using all four types yields ~78 bits entropy
- 4Rule of thumb: 60+ bits = strong, 80+ bits = very strong
"password" — 8 chars, lowercase only=Entropy ~37.6 bits — Very Weak
"P@ssw0rd" — 8 chars, all character types=Entropy ~52 bits — Fair
"xK#9mP2$nQ7!" — 12 chars, all types=Entropy ~78 bits — Very Strong
| Entropy (bits) | Strength | Est. Crack Time (offline) |
|---|---|---|
| < 28 | Very Weak | Instant |
| 28–35 | Weak | Minutes |
| 36–59 | Fair | Hours to Days |
| 60–79 | Strong | Years |
| 80+ | Very Strong | Centuries |
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